[en] This dissertation describes measurements of collisionless spin waves in liquid ³He in the normal and superfluid A₁, A, and B phases. The spin waves were measured by transverse cw NMR at the Larmor frequencies of 1,2, and 4 MHz. The pressure range was varied from 0 to12 bar. In the normal phase sharp peaks due to spin waves appear on the NMR line shape below 5 mK. These measurements were performed at several different field gradients. The experiment agrees quite well with a theory by Leggett (1970) and permits a determination of the Fermi liquid parameter F₁/sup a/. Although spin waves were observed in the A₁ phase, thus far there is no theory for their frequency and damping in this phase. In the A phase the spin waves were heavily damped except near T/sub c/. The peak frequency displays shifts which are not predicted by present theories. In the B phase the experiments agree at least qualitatively with the theory by Combescot (1975). The imaginary part of the diffusion coefficient in the B phase was determined from the experimental spin wave frequencies

[en] Accurate solutions of the Ginzburg-Landau equations describing the A-B phase boundary for a planar interface between ³He-A and ³He-B are calculated near the tricritical pressure and classified in terms of simple discrete symmetries. The order-parameter components of the A-B phase boundary and the interfacial energy σ/sub AB/(T) deviate considerably from previous variational calculations

[en] Superfluid liquid ³He is a unique system within condensed matter physics because it shows very sophisticated phenomena which are at the same time quite manageable theoretically. (orig.)

[en] Two major open problems in the behavior of superfluid ^He: the question of nucleation of the B-phase, and the dynamics of the ³He A-B interface, are examined. (H.W.). 80 refs.; 5 figs

[en] Experiments to see flow of superfluid Helium 3 are reported

[en] The sequence of events that led to the discovery of fluidity of ³He is outlined and the theory developed to account for this phenomenon is described. (Z.J.)

[en] The consequences of applying a BCS-like theory to the new A and B phases of superfluid ³He are discussed

[en] Research on ³He at very low temperatures is a vigorous and expanding field. Two years ago, two new phases of ³He were discovered at very low temperatures (about 0.002 degree above absolute zero). These phases have become known as anisotropic superfluids. A description is given here of some of the experimental evidence for the new phases and a simplified form of the theoretical model is presented. (9 figures, 25 references) (U.S.)

[en] The nonlinear reversible hydrodynamic equations for the superfluid phases of ³He, i.e., ³He-A, ³He-A₁, ³He-B, ³He-A in high magnetic fields, and ³He-B in high magnetic fields, are derived. The Mermin-Ho--type relations for ³He-A in high magnetic fields and ³He-B in high magnetic fields are given for the first time. The influence of higher-order gradient terms in all phases is discussed, and a new class of nonlinear terms containing the various kinds of velocities is given which have not been considered so far for any of the five superfluid phases. In addition we show that the hydrodynamic equations for ³He-A in high magnetic fields contain as a special case the hydrodynamics of superfluid ³He-A₁ and the orbit part of the hydrodynamic equations for ³He without external field. Furthermore, we point out some structural similarities in the equations for ³He-A in high magnetic fields and ³He-B in high magnetic fields. As an additional effect we find that the higher-order gradient terms imply a preferred direction in the hydrodynamic equations for superfluid ³He-B

[en] The author reports observations of the first-order phase transition between the two superfluid phases of ³He. A long cylindrical sample of the higher-temperature A phase is supercooled in a magnetic field within a simple dc magnetometer. B phase is then introduced at one end of the sample and its growth into the supercooled A phase is observed via the magnetometer signal. For temperatures above a certain value, T_nom, the phase interface travels up the tube at a fairly constant velocity, in reasonable agreement with the theory of Leggett and Yip. For temperatures below T_nom there arises a new interaction between the rapidly moving phase interface and the magnetization of the sample. These observations allow some characterization of this new interaction